1. Field of the Invention
The invention relates to a repairing method for a liquid crystal display panel, and more particularly, to a method for repairing an uneven defect on a liquid crystal display panel caused by a gravity issue.
2. Description of the Related Art
Since the progress of science and technology has led to small, effective, and portable intelligent information products, display devices have played an important role in modern society. In recent years, display devices have undergone great improvements in the areas of high performance, quality, larger size, and lower cost. TFT-LCDs have characteristics of thinness, lightness, and low power consumption, hence having the most chance to have a large market in the future as a display device to replace CRTs. Therefore, the large TFT-LCD panels used for television (TV) are popularized such as from 23″ to more than 100″ in diagonal size.
Generally, the liquid crystal display panel is erectly placed, hence the gravity will change the internal pressure balance around the bottom of the liquid crystal display panel, and will induce a visible defect, called gravity mura. And, the larger size of the liquid crystal display panels will have more chance to cause the gravity mura around the bottom of liquid crystal cavity within the liquid crystal display panel. Please refer to FIG. 1, which is a schematic diagram of an erectly placed liquid crystal display panel according to the prior art. The liquid crystal display panel 100 has two glass substrates 10 and 12, and the liquid crystal 16 is filled between the glass substrates 10 and 12 and is encapsulated by a closed sealant frame 14. When the liquid crystal display panel 100 is erectly placed, three kinds of forces, which are shown as F 1, F 2, and F 3 in FIG. 1, are exerted onto the bottom region 18 of the liquid crystal display panel 100. The arrows indicate the directions of F 1, F 2, and F 3.
The first force F 1 is caused by a pressure difference between the liquid crystal 16 in the liquid crystal display panel 100 and the outside environment. We can describe F 1 as following equation:F 1=ΔP
The second force F 2 is caused by the capillarity of the liquid crystal 16, and can be described as following equation:F 2=S·cos θ/d 
Where S is the surface tension of the LC medium inside the cavity, θ is the contact angle between the LC medium in cavity and the substrates of the panel, and d is the cell gap of the panel.
The third force F 3 is caused by the gravity of the liquid crystal. Defining the z-axis as zero at the top of the LC cavity of the TFT-LCD panel, and pointing downward as shown in FIG. 1. If bottom region 18 has a height of h along the z-axis from the top of the LC cavity of the TFT-LCD panel, then, F 3 can be described as following equation:F 3=ρ·g·h 
Where the ρ is the density of the liquid crystal medium within the LC cavity, g is the gravity constant on the earth surface, and h is the height of the bottom region 18.
At any given temperature, gravity mura won't occur at bottom region 18 under the condition, that isF 1+F 2≧F 3Hence, ΔP+S·cos θ/d≧ρ·g·h 
When the sum of the pulling forces F 1 and F 2 is larger than or equal to the pushing force of F 3, the liquid crystal 16 in the liquid crystal display panel 100 is in a pressure balanced condition, and the images can be normally displayed. If the sum of the pulling forces F 1 and F 2 is smaller than the pushing force of F 3, a gravity mura will happen at the bottom region 18 of the erectly placed liquid crystal display panel 100, and the image quality at the location of gravity mura is degraded.